A communication system such as the IBM 3725 or 3745 Communication Controller, comprises a central control unit CCU running a Network Control Program NCP stored in a memory, an I/O bus for connecting the central control unit CCU to end users through line adapters on the one hand, and to central processing units CPU through channel adapters on the other hand. U.S. Pat. No. 4,593,352 describes this system and the method for exchanging information and data on the I/O bus.
A communication controller such as the IBM 3745 is provided with a direct memory access capability, which allows attachment of high speed communication links T1 as described in EP-A-0 000244544.
Now, using switching systems such as described in EP-A-0 000387464, it will be possible to interconnect communication devices without the need of a central control unit.
In such an environment, it will be of interest to have one communication device made of a communication controller of the IBM 3745 type, so that the connectivity of this controller can be extended in a significant way.
However, because the Network Control Program is designed to be able to manage a maximum number of line adapters, such a connection is not possible.